Stances



surfaces through the pipe l. 'By this arrangement all 4rvasteor loss lofthe powdered, material is as much as possible avoided, since the largestquantity of dust or powder still oating in the current of airis drivenback .to the crushing-surfaces. i i

In the interior of the chambers F F is a series of screens, t t', madeof gauze, or other suitable material, und exten-ding clear'across thechambers at suitable intervals, By vthese screens the current of air iscompelled to spread uniformly throughout the chambers, and the dustsuspended in the air adheres tothe meshes of the screen, from Whichit iscaused to separate by imparting to said screens ashaking motion. Thismotion is producedby means of hooks u, which pass' down through the topsof the-chambers and catch in the screens, as

shown in iig. 3.

While passing through the chamber -F the air is almost entirely freedfrom dust,and'as this vairfenters the case ofthe fan-blower, a portionof it is forced back to the crush'er through the pipel, while thebalance passes through the pipe o into the chamber F whereitiscompletelyfreed from dust, and whence-the air escapes thrugh thepipep in the openatmosphere. If it should be found that the airthus escaping in thcatmosphere still carries with it some of the dust, agthird chamber maybe added. The small quantity of dust'carried back through the pipe l,between the crushing-surfaces, does not interfere with the crushingoperation, and it is sucked out'again through the pipe k. v

From this description it will'be seen that the air is made to circulatethrough .the apparatus, and the quantity of air escaping from the lastchamber, F', in the open atmosphere, fis equaltofthe quantity sucked'inlthrough the joints at the'Workiugsurfaces-of the. crushing-apparatus,which, of course, depends upon the con. dition of the packing-piecesapplied to keep saidjolints tight. Since this quantity of air cannot bedetermined in advance, the pipe o is provided withia valve, g, wherebythe area of its effective cross-section can be regulated tolcorrespondto the quantity of air admitted throughthe joints. If these jointscou-ld bemade perfectly air-tight, all the air would-.circulate throughthe apparatus -in a continuous current, and no portionthereof would be'permitted to escape in the open air.V A l It is obvious that thepneumatic apparatus hereinbefore described, together with the chambers,canlalso be' connected to a crushing-apparatus of any other constructionbesides that shown in the drawing, such, for instance, as stampers,crushing-rollers, cylindrical or conical crushing-wheels, and so forth,and it will be found 4that in all cases the working capacity of suchcrushing-apparatus will be materially improved. I

What'I claim as new, and desire to secure bylLetters Patent, is

1. The combination of the rake or scrapei'j, carriage D, Crusher B, bedC, and the lpneumatic apparatus, constructed aud operatingsubstantiallyas und for thepurpose described. I l

2. The lips or anges m n, extending overthe surfaces of thecrusl1er'B,.und bed C, substantially'as' and for the purpose described.v l

The above specification signed by me, this 31st day of January, 1867.

' F. E. HOFFMANN. [1.. s.]

Witnesses:

FRIEDRICH vz OPPEI., [1.. s] HERMANN RIEM. [1.. s]

